Nepheline syenite powder with controlled particle size and novel method of making same

ABSTRACT

An ultra-fine inorganic powder for use as a filler and formed from a hard, naturally occurring mined material, in particular nepheline syenite, where the powder has a targeted controlled maximum particle size of less than 5 microns and a generally uncontrolled minimum particle size.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a divisional application that claims priority onU.S. application Ser. No. 12/215,643 filed Jun. 27, 2008 (UMEE 2 00090(I); UNM-19913) and Provisional Application upon which it claimspriority, i.e. Ser. No. 60/958,757 filed Jul. 9, 2007 (UMEE 2 00090 P).These two applications and Publication No. 2009-0013905 (UMEE 2 00090(I); UNM-19913) published on Jan. 15, 2009 are hereby incorporated byreference herein.

Since this application merely claims a second inventive conceptdisclosed in prior copending application Ser. No. 12/215,643, it is adivisional application based upon said prior application. Informationexpressing the statement of invention and objects of the new claimedinvention has replaced the statement of invention and objects of theprior claimed invention. Furthermore some unnecessary and irrelevantpassages have been removed. This application does not include any newmatter.

THE NEPHELINE SYENITE INDUSTRY

The present invention relates to the art of fine grain nepheline syenitepowder as a category in the nepheline syenite industry and moreparticularly to a novel “ultra-fine” nepheline syenite powder havingcontrolled particle size and the method of making this novel ultra-finenepheline syenite powder. Coatings and films using the novel ultra-finenepheline syenite powder constitute a further aspect of this invention.

Unimin Corporation of New Canaan, Conn. is a leading source of mined rawnepheline syenite, which is a natural occurring rock formed from severalminerals and is found in deposits in only limited areas of the world.Nepheline syenite is an rock having feldspar as its major mineral andsubstantially no free silica. More particularly, Nepheline syenite isnaturally occurring rock constituting a mixture of Na feldspar, Kfeldspar and nepheline. (NaAISiO4). It has a low level of free silicondioxide. This material can be described as either syenitic and/orsyenitic feldspar. Nepheline syenite can have about 99% feldspar and canbe formed by more than one feldspar. The nepheline syenite industry hasdeveloped technology that is used for grinding and crushing rawnepheline syenite rock and then converting the particulated nephelinesyenite into usable fine grain powder. Thus, the field to which thepresent invention is directed is the industry of nepheline syenite andthe technology of converting nepheline syenite as mined into usable formthat is a commercial powder. In about 2001, Unimin Corporation, aftersubstantial research and development, invented an ultra-fine nephelinesyenite powder, which powder was believed to be the smallestcommercially available and economically producible nepheline syenitepowder. This was the first ultra-fine nepheline syenite powder and wassold under the trademark Minex 10. This powder had a maximum particle orgrain size D99 substantially above 15 microns. However, it wasclassified as “ultra-fine” nepheline syenite powder because it had amaximum particle size of less than about 20 microns. However, in someinstances maximum particle size is referred to as the D95 value. Minex10 was the smallest nepheline syenite powder available to the market formany years. Such “ultra-fine” nepheline syenite powder had the smallestcommercially available grain size. After years of research anddevelopment Unimin Corporation, again using its expertise and know-howacquired at extremely high cost over many years of work by its employeesinvented a novel version of ultra-fine nepheline syenite powder. Thisnew ultra-fine nepheline syenite powder had a maximum grain size D99 ofless than 10 microns, which was the size believed at that time to beunobtainable for commercial production. Such smaller grain sizeultra-fine nepheline syenite powder was found to create drasticallydifferent physical characteristics and properties in certain commercialproducts, such as coatings and films. Consequently, the recentlyinvented nepheline syenite powder that imparted improved, albeitdifferent physical characteristics and properties to many end productswas believed to be the ultimate in nepheline syenite powder, especiallyfor coatings and films. This powder created a new art for usingnaturally occurring materials and is the art to which the presentinvention is directed. This newly developed ultra-fine nepheline syenitepowder has now been introduced into the market under the trademark Minex12. Prior to Minex 12 the only other commercially available ultra-finenepheline syenite powder was sold as Minex 7 or Minex 10. Minex 7 havinga maximum grain size D99 of about 20 microns and was “ultra-fine” asthis term is used herein and used in the art of the present invention.Minex 7, Minex 10 and Minex 12 are classified as ultra-fine nephelinesyenite powders and are the commercially available nepheline syenitepowders to which the present invention is an improvement.

A larger nepheline syenite powder, which is greater than “ultra-fine”grade, is Minex 4 having a maximum grain size D99 of about 40 micronsand a D99.9 grain size of about 60 microns. All these commerciallyavailable nepheline syenite powders define prior art to the inventionand form the background to which the present invention is directed. Theart is nepheline syenite powder as an area in the nepheline syeniteindustry. After Minex 12, with a maximum grain size D99 of less than 10microns was introduced as the commercial nepheline syenite powder, itwas determined that this extremely small ultra-fine nepheline syenitepowder imparted substantial advantages to a large variety of commercialproducts including coatings, films, and inks, to name a few. These sameproperties are also realized by use of the present invention. Tocomplete the background of the nepheline syenite powder art, prior U.S.patent application Ser. No. 11/803,093, filed on May 11, 2007 (UMEE 200075) is incorporated herein as background information for the varioususes of “ultra-fine” nepheline syenite powder, which is theclassification of the powder to which the present invention is directed.The present invention is an improvement and substantial advance in theart of nepheline syenite powder and in the sub-art of “ultra-fine”nepheline syenite powder which is a powder having a maximum grain sizeD99 of generally less than about 20 microns. In view of this background,this application relates to the specific processes used to produce anovel ultra-fine nepheline syenite powder, which novel powder is used inseveral applications found to be uniquely enhanced by ultra-finenepheline syenite powder, such applications as coatings of the clear,ultra violet cured, hard, semi-transparent, and powdered types. Thisapplication discloses a novel “ultra-fine” nepheline syenite powder, thenovel method of producing this novel ultra-fine nepheline syenite powderand the coatings and films using such novel ultra-fine nepheline syenitepowder.

Nepheline Syenite Background Information

The present invention relates to the nepheline syenite powder art;however, before describing the advance constituting the invention of thepresent application, a general understanding of the nepheline syeniteindustry itself as evidenced by the patented technology will illustratethe difference between the general nepheline syenite industry and thespecific art of the present invention, which art is commercial gradenepheline syenite powder and particularly ultra-fine nepheline syenitepowder.

Standard ground nepheline syenite in particulate form has been acommercial product for many years. Indeed, nepheline syenite powder inparticulated form has been used extensively to make industrial compoundsand to instill enhanced properties in liquid coatings, ceramics, glass,etc. For illustrations of representative products or compounds employingstandard processed particulate nepheline syenite, the following U.S.patents are incorporated by reference. Consequently, the generalproperties and procedures for using existing nepheline syenite particlesneed not be repeated.

Koenig 2,261,884 use as flux in ceramic Lyle 2,262,951 color ingredientin glass Thiess 2,478,645 porcelain glaze Hummel 2,871,132 glazingcompound Huffcut 3,389,002 heat and corrosion resistant coating Weyand3,486,706 binder for grinding agent Waters 3,917,489 ceramic flux Harris3,998,624 source of metal aluminum silicate Brown 4,028,289 inorganicfiller Chastant 4,130,423 natural silicate for slag formation Funk4,183,760 alumina ceramic Aishima 4,242,251 alumina silicate fillerSeeney 4,396,431 inorganic binder Drolet 4,468,473 SiO₂ source Shoemaker4,639,576 electrode coating Goguen 4,640,797 polymer filler Vajs4,743,625 vitrifying material Holcombe 5,066,330 refractory filler Kohut5,153,155 non-plastic filler Slagter 6,569,923 polymer cement White6,790,904 liquid coating

Other uses of standard, ground nepheline syenite have been recentlysuggested. Representative examples of such newer applications of groundnepheline syenite are disclosed in the following United States patentpublications:

Schneider 2002/0137872 scratch resistant coating Zarnoch 2002/0173597filler in resin powder Fenske 2003/0056696 filler for polymer cementBurnell 2003/0085383 suspending filler Burnell 2003/0085384 heat curableresin White 2003/0224174 filler in liquid coating Schneider 2003/0229157scratch resistant powder coating Giles 2004/0068048 filler for rubberFinch 2005/0059765 filler for plastic coating Adamo 2005/0214534extender for curable composition Duenckel 2006/0081371 sintering aidSchneider 2006/0160930 corrosion resistant coating Dorgan 2006/0235113filler for polymer

Ground nepheline syenite and larger grain nepheline syenite powder areused as a filler or extender in paints, coatings, plastics and paper. Itis a desirable material because it contains virtually no free silica andstill functions as effectively as a free silica based filler orextender. Nepheline syenite is an inorganic material that is a naturallyoccurring mined substance having substantially no free silica and whichis hard since it has a Mohs number of 6. The material is an inorganicoxide having mechanical characteristics similar to the free silicamaterials for which it is used as a substitute in various industries.These mechanical properties of ground nepheline syenite are realized bythe use of a fine grain particulate form of nepheline syenite, which issometimes a powder that has a grain size greater than about 15-60microns. These known ground and powdered nepheline syenite products arequite abrasive for manufacturing equipment. Consequently, the granularnepheline syenite has a high tendency to abrade and erode quite rapidlyequipment used in processing the various compounds, even compoundsincorporating the fine grain powder of the prior art. It has beendetermined that by reducing the fine grain size of any inorganic oxidematerial, such as nepheline syenite, the abrasive properties of thematerial are reduced. It is common to provide ground nepheline syenitewith a relatively small grain size for the purpose of allowing effectivedispersion of the product aided by the use of nepheline syenite powder.The advantage of dispersing fine grain nepheline syenite in the carrierproduct is discussed in several patents, such as Gundlach U.S. Pat. Nos.5,380,356; Humphrey 5,530,057; Hermele 5,686,507; Broome 6,074,474; and,McCrary Publication No. US 2005/0019574. These representative patentpublications show fine grain nepheline syenite and are incorporated byreference herein as background information regarding the presentinvention. These disclosures illustrate the advantages of providing thisinorganic oxide in a very fine grain size for a variety of applications.In US Publication 2005/00019574 there is a discussion thatmicrocrystalline silica is a preferred filler in plastic. Groundnepheline syenite from Unimin Corporation, New Canaan, Conn., is thusprovided as a fine grain silica deficient silicate in the form of asodium potassium alumino silicate. The particles of this nephelinesyenite are finely divided and have a grain size in the range of about 2to about 60 microns. This widely used commercial product having thisgrain size and wide particle size distributions has been sold as anadditive that provides the nepheline syenite properties.

SUMMARY OF BACKGROUND

The present invention relates to the unique technique of producingultra-fine powder from nepheline syenite a naturally occurring igneousrock containing substantially no free silica and which is hard since ithas a Mohs number of 6. This technology advance has resulted from adesire to produce ultra-fine nepheline syenite powder having a verysmall maximum particle size. Nepheline syenite powder is relativelyinexpensive, hard and free of silica composite rock; consequently, itpresents tremendous benefits for fillers in coatings and films. Suchproducts utilize the nepheline syenite powder as an extender or fillerto impart unique physical characteristics to coatings, films or otherthin substrates. Over many years substantial research and development byUnimin Corporation, assignee of this application, the leader in thenepheline syenite industry was able to produce only a commerciallyviable nepheline syenite powder having a maximum particle size, usuallyreferred to as the D99 particle size, of over about 15 microns. Thispowder was believed by the industry to be the finest commercial versionof nepheline syenite powder. Such small ultra-fine powder was sold underthe trademark Minex 10 and gained substantially commercial acceptancebecause of the unique properties of the material and its small size. Itwas “ultra-fine” which is defined as having a maximum particle size D99of less than 20 microns.

STATEMENT OF INVENTION

After tremendous commercial success of the Minex 10 nepheline syenitepowder, Unimin Corporation invested substantial expense and research anddevelopment time directed toward inventing a commercially viablenepheline syenite powder which would have a controlled maximum particlesize of less than 15 microns, but could still be manufactured and soldat a competitive price to the ultimate users. In this way, the hardnepheline syenite powder would be ultra-fine and would have a maximumparticle size at a level that drastically reduced the wear of equipmentemployed in producing the coating or film. With this objective ofproducing an improved commercial nepheline syenite powder in theultra-fine nepheline syenite industry, Unimin developed a new nephelinesyenite powder as disclosed in U.S. application Ser. No. 11/703,384filed Feb. 7, 2007 with an application No. 2 008-0015104 published onJan. 17, 2008.

The present invention is the result of a further research anddevelopment by Unimin Corporation wherein the maximum particle size D99of the ultra-fine nepheline syenite powder has been reduced to a D99value of less than 5 microns. This new product, which is the subject inthis application, has tremendous improvement over all prior ultra-finenepheline syenite powders. Consequently, nepheline syenite powder withall of its commercial advantages can be used as a substitute for nanofillers heretofore produced chemically and at great expense. The presentinvention is directed toward a naturally occurring mined powder thatcontains a feldspar and, preferably, to a nepheline syenite powderhaving the smallest maximum particle size D99 now obtainable in theindustry.

Parent application Ser. No. 12/215,643 filed Jun. 27, 2008 discloses theresult of the aforementioned research and development program conductedby Unimin Corporation, which program resulted in various inventions inthe nepheline syenite powder technology. In the parent application theparticular invention claimed was the primary aspect of the research anddevelopment project. This primary aspect was a unique ultra-finenepheline syenite powder having a top cut of less than 20 microns and abottom cut in the general range of 2-7 microns. The various newlydiscovered nepheline syenite powders of this project had unique physicalproperties and presented substantial and distinct advantages. Thepresent application is a divisional of the parent application andrelates to another or second invention made during the research anddevelopment project disclosed in the parent application. Thisalternative invention relates to an ultra-fine nepheline syenite powderhaving a targeted maximum particle size that is controlled to a targetedvalue of less than 5 microns. This alternative or second invention isdefined in the claims of this divisional application and presents asecond commercially viable and producible ultra-fine nepheline syenitepowder invented at Unimin Corporation. Indeed, this second novel powderhad nano size particles since the maximum particle size is less than 5microns. Examples of this second novel powder have a targeted maximumparticle size of 2 microns and 4 microns. The advantages of this secondinvention described in the parent application are documented herein.

In accordance with the present invention, there is provided anultra-fine nepheline syenite powder. This powder has a targetedcontrolled maximum particle size of less than 5 microns (for instance 4microns and 2 microns) and a generally uncontrolled minimum particlesize, thus, creating a targeted minimum particle size of 0 microns. Thispowder is described herein as the “−5” nepheline syenite powdersdeveloped by assignee in its disclosed research and development program.Embodiments of this invention are powders having a targeted maximumparticle size of 2 microns or a targeted maximum size of 4 microns. Ineach case, the targeted maximum size is less than 5 microns. The maximumparticle size is generally defined as a D99 particle size or morepractical, the D95 particle size.

In accordance with the present invention, there is provided anultra-fine inorganic powder formed from a hard, naturally occurringmined material having substantially no free silica, the powder having atargeted controlled maximum particle size of less than 5 microns and agenerally uncontrolled minimum particle size creating a targeted minimumparticle size of zero microns.

In accordance with other aspects of the present invention, there isprovided an ultra-fine nepheline syenite powder having a maximumparticle size D99 of less than 5 microns and preferably in the range of2-4 microns. Such particles have not heretofore been known in thenepheline syenite field of technology.

In accordance with another aspect of the present invention, the novelvery small ultra-fine nepheline syenite powder is produced by using awet mode of operation for producing the grinding of the particles in avertical stirred mill.

In accordance with another aspect of the present invention, the novelvery small ultra-fine nepheline syenite powder of the present inventionis produced by a pre-processed nepheline syenite powder with a maximumparticle size D99 in the range of 20-100 microns. Furthermore, thefeedstock has a moisture content of less than 0.8% by weight.Consequently, the new nepheline syenite powder defined in the claims ofthis application is produced from a pre-processed nepheline syenitepowder which in many instances is a commercial Minex powder produced andsold by Unimin Corporation.

In accordance with another aspect of the present invention, the novelpowder defined above has a particle size distribution with a narrowparticle size spread between the D99 particle size and the D1 particlesize. This narrow particle size spread is in the general range of 2-4microns.

In accordance with still another aspect of the present invention, thereis provided a method for making an ultra-fine nepheline syenite powdercomprising providing a feedstock of pre-processed nepheline syenitepowder, milling the feedstock into an intermediate powder, and airclassifying the intermediate powder to a targeted particle size D99 ofless than 5 microns. This method is preferably milled in a wet mode in avertical stirred mill; however, it is also milled in a jet mill wherethe jet mill is preferably a fluid bed opposed flow jet mill.

In accordance with another aspect of the present invention, thenepheline syenite powder has a controlled maximum particle size of lessthan 5 microns and preferably a D99 particle size in the range of about2-4 microns to impart a specific, very distinct characteristic to thecoating or film using the novel powder of the present invention.

The primary aspect of the present invention is provision of anultra-fine nepheline syenite powder having a substantially controlled,or targeted, very small maximum particle size of less than 5 microns. Bycontrolling the maximum particle size of the nepheline syenite powder,the range of distribution of particle size is made quite narrow toimpart distinct and repeatable physical characteristics to the coatingsand/or films utilized in the present invention.

In accordance with another aspect of the present invention, theultra-fine nepheline syenite powder of the present invention has acontrolled maximum particle size of less than 5 microns, and is producedby utilizing a pre-processed nepheline syenite feedstock that ispreferably a commercial pre-processed nepheline syenite powder, such asMinex 7 and Minex 10. The novel ultra-fine nepheline syenite powder ofthe present invention has a moisture content less than 0.8% by weightand a narrow particle size range between the D1 particle size and theD99 particle size. Consequently, the distribution of particles is a verynarrow range to give consistent and well defined physicalcharacteristics to coatings and films or any other product using thisnew ultra-fine nepheline syenite powder.

In accordance with the invention, the new ultra-fine nepheline syenitepowder has a controlled “targeted” maximum particle size, which isusually defined as a D99 particle size. The term “target value” or“targeted” is a value imparted to the maximum grain size in accordancewith the practical applications of the present invention. As known inthe relevant technologies, the exact maximum particle size may varyunintentionally from the targeted value that is used to define the metesand bounds of the present invention.

In yet a further aspect of the present invention, the nepheline syenitefeedstock is processed by an air classifier. Indeed, the novelultra-fine nepheline syenite powder is formed by various processes, oneinvolving air classification. The other involving a series of airclassifiers and the other a mill and air classifier in seriesconstituting a continuous process. In accordance with an aspect of thepresent invention, the mill used in one method for producing theultra-fine nepheline syenite powder of the present invention is an airjet mill. Furthermore, the smaller embodiment of the present invention,such as the 0×2 powder, is produced by a vertical stirred mill with orwithout grinding aids. Furthermore, in making this embodiment of theinvention, the vertical stirred mill is operated in a wet mode; however,it can be operated in a dry mode as can the opposed jet mill, especiallyfor larger maximum particle sizes, such as the 0×4 powder example.

Nepheline syenite is a naturally occurring rock constituting a mixtureof sodium feldspar, potassium feldspar and nepheline (Na Al SiO4). Thismaterial is substantially free of silica dioxide. Furthermore, thismaterial can be described as either syenite or syenite feldspar.Consequently, the present invention is applicable to nepheline syeniteand also other syenite materials having drastically low free silicondioxide. The general description of nepheline syenite is applicable toan understanding of the present invention and is used to define thenepheline syenite rock formation constituting the material used inpracticing the invention.

The invention comprises a unique “ultra-fine” nepheline syenite powder,new and novel methods of making such powders, use of the powder as afilter for coatings and films and the coatings or films using the novelnepheline syenite powder.

The present invention relates to controlling particle size distributionand particle size upper limits in systems of nepheline syeniteparticles. Although efforts have been undertaken in the prior art toproduce nepheline syenite powder with a generally reduced particle size,artisans in the related field have not recognized the many benefits thephysical properties that can be realized from a very low controlledmaximum particle size for the nepheline syenite powder, i.e. a D99particle size of less than 5 microns and generally in the range of 2-4microns.

The present invention provides a nepheline syenite particle systemexhibiting a very low abrasiveness. Indeed, the Einlehner value of thepresent invention is a number substantially less than 50. The presentinvention provides a nepheline syenite particle system exhibiting a verylow gloss and extremely beneficial optical characteristics.

The present invention also relates to numerous products and applicationsmade possible by the use of the nepheline syenite particle systemconstituting this aspect of the present invention. The use andincorporation of the various particle systems described herein providenew strategies and applications for nepheline syenite powder.

An object of the present invention is the provision of a filler forcoatings and films, which filler is an ultra-fine nepheline syenitepowder produced from pre-processed nepheline syenite powder. In this newpowder the maximum particle size is controlled to a given value therebyreducing abrasive properties of the filler. The new ultra-fine nephelinesyenite powder shows low gloss and less abrasion to processing orapplication equipment. These properties of the novel filler, produced inaccordance with this object of the present invention improves thecoating hardness and abrasive resistance of the coating and producesdistinct properties in the coating or film because of the very lowcontrolled maximum particle size of the nepheline syenite powder.

Another object of the present invention is the provision of anultra-fine nepheline syenite powder, which powder has a controlledmaximum particle size not heretofore obtainable in the nepheline syenitepowder industry. This controlled maximum particle size is less than 5microns and preferably in the general range of 2-4 microns.

Another object of the present invention is the provision of a uniquenovel method of producing the novel ultra-fine nepheline syenite powderhaving a controlled maximum particle size with values less than 5microns.

Still a further object of the present invention is the provision of afiller utilizing the novel nepheline syenite powder, as defined above,which filler is employed in coatings and/or films to produce a novelcoating or film with distinct physical characteristics.

Yet another object of the present invention is the provision of a novelultra-fine nepheline syenite powder having a controlled particle sizedistribution defined by a very low maximum particle size. By having anovel particle size distribution in the range of 0 microns to less than5 microns (such as 4 microns), the powder has a very low abrasivecharacteristic for manufacturing equipment and a drastically improvedrepeatability of properties imparted by the filler in the product usingthe inventive nepheline syenite powder.

Yet another object of the present invention is the provision of a methodof forming the ultra-fine nepheline syenite powder described above,which powder are characterized by having a relatively small particlesize diameter D99 and a relatively narrow particle size distributionbetween the D99 particle size and the D1 particle size.

Still a further object of the present invention is the provision of anultra-fine nepheline syenite powder with a controlled grain sizedistribution that is a highly bright material usable for fillerapplications and in clear coatings. The unique novel nepheline syenitepowder of the present invention can be formed into a concentrate andthen dispersed into a coating or other matrix material and has adrastically decreased settling tendency.

Still another object of the present invention is the provision of anultra-fine nepheline syenite powder with a controlled particle sizedistribution, which powder, when used for ultra-violet, clear orsemi-transparent coatings, results in a superior clarity compared tocompetitive filters, can be used with up to 20-25% loading, is UVtransparent, is easily dispersed into low viscosity systems andincreases film hardness and scratch resistance. By the control of theparticle size distribution to a low level, these properties in thecoating are unique and can be duplicated by subsequent use of the noveland defined particle size controlled ultra-fine nepheline syenite powderof the invention.

Yet a further object of the present invention is a novel ultra-finenepheline syenite powder, as defined, which powder, when used in acoating, retains weathering durability increases hardness and blockresistance for kitchen and appliances applications and offers highergloss than large grain size nepheline syenite powder.

The novel nepheline syenite powder has a controlled maximum particlesize to minimize abrasion and equipment wear and has superiorcost/performance balance versus expensive “nano” fillers. The presentnepheline syenite powder is a direct competitor to such nano fillers andimparts the advantages of nepheline syenite powder to a filler used as asubstitute for the expensive, chemically produced nano fillers.

Yet another object of the present invention is the provision of acoating containing the novel ultra-fine nepheline syenite powder, whichcoating is clear, hard and resistant to scratches. This novel filler isrelatively inexpensive as compared to other nano fillers. Coatings usingthe new ultra-fine nepheline syenite powder as a filler is curable byexposure to ultra-violet radiation (i.e. is UV curable). Consequently,the coating using the novel ultra-fine nepheline syenite powder isreliably curable and curable in a repeatable fashion due to the controlparticle size distribution of the present invention.

All of these objects and advantages and the statements of the presentinvention have been determined experimentally and tested to allowdescription of the physical characteristics imparted by the novelultra-fine nepheline syenite powder to products, such as coatings andfilms. These advantageous properties are repeatable because of the nanoparticle size distribution of the novel ultra-fine nepheline syenitepowder. The coatings or films are inexpensive due to the fact that thisvery small, novel nepheline syenite powder can be easily dispersed athigh loadings in coatings and films. Furthermore this new nephelinesyenite powder has substantially no free silica, which characteristic ofnepheline syenite is another advantage of the novel “ultra-fine”nepheline syenite powder. This is especially important for an ultra-finepowder that can become air borne during subsequent handling andprocessing.

Still a further object of the present invention is the provision of anultra-fine powder used as a filler, which filler has a novel controlledmaximum particle size and is derived from naturally occurring blockformations.

These and other objects and advantages are part of the disclosure andwill become more apparent in the following description taken togetherwith the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow chart schematically illustrating a method for producingthe novel ultra-fine nepheline syenite powders;

FIG. 2 is a block diagram of a method of producing the claimed nephelinesyenite powder of the parent application from either Minex 4 or Minex 7;

FIG. 3 is a block diagram of the method of producing one version of theultra-fine nepheline syenite powder claimed in the parent applicationwhere the feedstock has the desired controlled maximum particle size;

FIG. 4 is a block diagram schematically illustrating a method ofproducing a version of the ultra-fine nepheline syenite powder claimedin this divisional application;

FIG. 5 is a schematic and flow chart of the method produced by theequipment schematically illustrated in FIG. 1;

FIG. 6 is a table of the target particle sizes of several samples ofultra-fine nepheline syenite powder, including nepheline syenite powderin accordance with the present invention and setting forth the particlesize distribution between D1 and D99.9 where the target values are D5and D99 of the samples;

FIG. 7 is a graph illustrating nominal sizes of samples described in thetable of FIG. 6 and illustrating the targeted grain sizes of theultra-fine nepheline syenite powder samples, including novel powders ofthe present invention;

FIG. 8 is a graph of various particle size distributions of nephelinesyenite particles having no controlled minimum particle size as insamples defined in the graph of FIG. 7 and the table of FIG. 6;

FIG. 9 is a graph of particle size distribution for samples havingnominal 2 micron minimum particle size;

FIG. 10 is a graph similar to FIG. 9 illustrating an ultra-finenepheline syenite powder with a controlled minimum grain size of 4-6microns;

FIG. 11 is a graph of the average contrast ratio of black and white testpanels having coatings with various known and preferred embodiments ofthe present invention;

FIG. 12 is a graph of 20° gloss of powder coatings with various knownand preferred embodiments of the present invention;

FIG. 13 is a block diagram of a second preferred embodiment of aninventive method for producing ultra-fine nepheline syenite powderhaving the characteristics of a novel powder;

FIG. 13A is a schematic diagram of an opposed air jet mill of the typeused in practicing the method described in FIG. 13;

FIG. 14 is a block diagram like the diagram of FIG. 13 showing thesecond preferred method for producing ultra-fine nepheline syenitepowder of the parent application showing use of a generic dry mill andan additional process to make a small particle size powder with only acontrolled maximum particle size as on this divisional application;

FIG. 15 is a block diagram schematically illustrating another method ofproducing nepheline syenite powder with a targeted grain size of 5×15and alternatively 6×15;

FIG. 16 is a block diagram similar to the block diagram of FIG. 14illustrating a method for producing ultra-fine nepheline syenite powder,wherein the target grain size is 5×15 and where the powder is producedby removing only the lower particle sizes from the feedstock having adesired controlled maximum grain size;

FIG. 17 is a graph representing ultra-fine nepheline syenite powdersproduced by the method disclosed in FIG. 16;

FIG. 18 is a graph similar to FIG. 17 describing ultra-fine nephelinesyenite powders produced by using the method schematically illustratedin FIG. 15; and,

FIG. 19 is a chart showing particle size distribution curves for samples(9)-(11).

Having thus defined the drawings, further features of the invention willbe hereinafter described.

The advantages of the present invention, i.e. the novel “ultra-fine”nepheline powder having certain particle size distributions, are, inaddition to and sometimes duplicative of, the advantages discussed inthe introductory portion of the present disclosure. The disclosuresestablish the merit of various aspects of the present invention. Indeed,there are distinct advantages of using the nepheline syenite powder andsystems described herein in certain coatings and other products.Nepheline syenite powder having a grain size of less than about 15microns is known, but controlling the particle size distribution asdescribed herein is not known. There was little known about thetremendous combinations of properties and characteristics to be impartedto products by the novel grain size distributions and control ofparticle sizes of the present invention. The concept of controlling thegrain size of nepheline syenite powder, again this invention, was notpursued and the advantages were not realized until the present inventiveact.

Preferred Particle Systems

It is instructive to explain certain designations and nomenclaturedescribed herein. Particle sizes, unless indicated otherwise, are givenin microns, 10⁻⁶ meters. As will be appreciated by those skilled in theart, particle sizes are expressed in diameters. Although diameters implya spherical or round shape, the term diameter as used herein also refersto the span or maximum width of a particle that is not spherical.Typically, ranges of particle sizes or size distributions are noted. Forexample, for a range of 2 to 10 microns, a designation of “2×10” istypically used. Also, if no lower size limit is designated for the rangeat issue, the collection of particles is referred to as “minus” and thenthe upper size limit is noted. Thus, for example, for a collection ofparticles having no lower size limit and an upper size limit of lessthan 5 microns, the designation “minus 5” or “−5” is used. Anotherdesignation used herein is “D_(n)” where n is some numerical valuebetween 0 and 100. This value refers to a proportion or percentile ofparticles having a certain maximum diameter. For example, in a particlepopulation having a target size of 0 to 18 microns, for instance, themedian maximum diameter (D50) may be 2.5 microns, the largest diameterin the 99^(th) percentile of the population (D99) may be 16 microns, andthe largest diameter in the 1^(st) percentile of the population (D1) maybe 0.1 microns. These values, particularly when taken collectively,provide an indication as to the “spread” or distribution of particlesizes in the particular system. The spread is preferably between D95 andD5, but it can be between D5 and D99 or D1 and D99.

Certain nepheline syenite particle systems with particular sizedistributions and characteristics have been discovered. The preferredembodiments nepheline syenite particle systems of the invention claimedin the parent application are a 2×10 system, a 4×15 system, a 5×15system, and 6×15 system. These systems exhibit surprisingly andunexpected beneficial physical properties including, but not limited toreduced abrasiveness, reduced gloss, and increased hardness and reducefriction, lower oil absorption for higher loading and better rheology.Tables 1-4 set forth below, present typical, preferred, and mostpreferred values for the D1, D50, and D99 size characteristics ofvarious preferred embodiment nepheline syenite particle systems inaccordance with the invention claimed in the parent application. Allparticle sizes noted are in microns.

TABLE 1 2 × 10 Preferred Embodiment Particle System D₁ D₅₀ D₉₉ Typical0.2-2.6 2.9-4.7 8.1-10.9 Preferred 0.3-2.3 3.3-4.3 8.5-10.5 MostPreferred 0.8-1.8 3.8 9.0-10.0

TABLE 2 4 × 15 Preferred Embodiment Particle System D₁ D₅₀ D₉₉ Typical0.9-3.7 7.9-9.7 14.3-17.1 Preferred 1.3-3.3 8.3-9.3 14.7-16.7 MostPreferred 1.8-2.8 8.8 15.2-16.2

TABLE 3 5 × 15 Preferred Embodiment Particle System D₁ D₅₀ D₉₉ Typical3.3-6.1 8.4-10.4 14.6-17.5 Preferred 3.7-5.7 8.9-9.9  15.1-17.1 MostPreferred 4.2-5.2 9.4 15.6-16.6

TABLE 4 6 × 15 Preferred Embodiment Particle System D₁ D₅₀ D₉₉ Typical3.1-5.9 9.1-11.1 16.5-19.4 Preferred 3.5-5.5 9.6-10.6 16.9-18.9 MostPreferred 4.0-5.0 10.1 17.4-18.4

Significantly reduced abrasiveness of nepheline syenite particle systemscan be obtained by using particle systems having a relatively smallparticle size for the upper size limit, and a relatively “tight”particle size distribution. For example, in one embodiment, the systemhas a median or D50 size of 8-11 microns, a lower or D1 size limit of2-5 microns, and an upper or D99 size limit of 15-19 microns. Thisembodiment particle system exhibits an Einlehner value of 180-200. Inanother embodiment particle system, the system has a D50 size of 3-4microns, a D1 size limit of 1-2 microns, and a D99 size limit of 9-10microns. This system exhibits an Einlehner value of 70-90.

Significantly reduced gloss and frequently while maintaining clarity canbe achieved by use of certain embodiment particle systems describedherein. An embodiment particle system having a D50 size of 8-11 microns,a D1 size of 2-5 microns, and a D99 size of 15-18 microns, exhibits a 20degree gloss of less than 50, and preferably 40-50, and a 60 degreegloss of less than 95 and preferably 80-95.

Equipment Used to Produce Powder

A method for forming the various particle systems described herein is byuse of a vertical stirred ball mill, also sometimes referred to as anattrition mill in the industry. Such a mill is commercially availablefrom Union Process Attritor Co. in Akron, Ohio and is illustrated inU.S. patents, such as U.S. Pat. Nos. 4,850,541 and 4,979,686, which areboth incorporated by reference herein.

Generally, three types of Attritors are available—a batch Attritor, acontinuous Attritor, and a circulation grinding Attritor.

The batch Attritor consists of a jacketed vessel filled with grindingmedia. Either hot or cold water or low pressure steam is run through thespecially designed jacket for temperature control.

Production size Attritors are equipped with a built-in pumping systemwhich maintains circulation during grinding for accelerated attritionand uniformity. The pump can also be used for discharging.

In the batch Attritor, the material is fed into the jacketed tank and isground until the dispersion and desired particle size are achieved. Nopremix is necessary as it is accomplished in the grinding chamber.Ingredients can be added at any time. Inspection and formula correctionscan be made during the grinding process without stopping the machine.

The Model 01 Attritor available from Union Process Attritor Co. is avery useful research tool for testing various formulations and grindingconditions. The lab model 1-S can be used for an accurate scale-up testmachine. The most important factor is to keep the peripheral tip speedconstant and the media to slurry ratio about the same. Generally in the1-S, the media/slurry ratio is 1:3/4, but in the production unit it is1:1, therefore grinding times are somewhat longer in the largermachines, such as the 200-S and 400-S.

Another system is the continuous Attritor (C or H machine) which isbest-suited for continuous, large production quantities. The continuousAttritor has a tall, narrow, jacketed tank into which a well premixedslurry is pumped in through the bottom and discharged at the top. Gridslocated at both the bottom and top of the machine retain the media.

The fineness of the processed material depends on the residence or“dwell time,” which is defined as the length of time the material to beprocessed stays in the grinding chamber.

The dwell time is controlled by the pumping rate. The slower the pumpingrate, the longer the dwell time, and hence the finer the grind.

The dwell time is calculated by dividing the void volume by the pumpingrate. Void volume is the entire volume of the tank minus the media andthe agitator shaft and arms. Therefore, scale-up for a “C” machine isdetermined by calculating the dwell time of a particular product anddividing this into the void volume of the larger unit. This is assumingthe same tip speeds for both units. For quick scale-up, one can ratiothe gross tank capacities.

One prerequisite of the continuous Attritor is that it needs a wellmixed, uniform, homogeneous feed. Also a good metering pump is required,such as a gear or moyno pump.

The continuous Attritor can be set up in series. By using larger mediain the first unit, which is equipped with grids having larger openings,the system can accept a coarser feed size. The subsequent units can havesmaller media, resulting in a finer grind.

Another system to produce novel powder uses a device called thecirculation grinding Attritor (Q machine) and has been developed in thelast few years. This system is a combination of an Attritor and a largeholding tank which is generally 10 times the size of the attritor. TheAttritor is filled with media and contains grids which, as in thecontinuous Attritor system, restrain the media while the slurry isallowed to pass through.

One of the essential requirements of the Q Attritor is the highcirculating (pumping) rate. The entire contents of the holding tank arepassed through the Attritor at least once every 7½ minutes, or about 8times per hour.

This high pumping rate results in a faster grind and a narrower particlesize distribution. This phenomenon is explained by the principle ofpreferential grinding. The fast pumping stream through the agitatedmedia bed makes the Q-machine grinding chamber act as a dynamic sieve orfilter, allowing the fines to pass and move quickly through, while thecoarser particles follow a more tortuous path through the media bed.

With the circulation process, unlike the continuous attritor with theslurry making a single pass, the material makes many passes through thegrinding chamber until the desired particle size is obtained.

Generally a gear pump is used which is a good metering pump. However,for abrasive and high viscosity slurries, a diaphragm or moyno pump isused.

It may also be preferred, in certain applications to use one or moregrinding aids when forming the preferred embodiment particle systemsdescribed herein. Representative examples of such particle systemsinclude, but are not limited to tri-ethanolamine, ethyl alcohol, aceticacid, silicone glycol surfactants, and combinations thereof. Of these,tri-ethanolamine is preferred.

Using an attrition mill produces a powder that can be used to practicethe invention. The output powder is processed into a system of nephelinesyenite particles having a relatively small size and a relatively narrowparticle size distribution can be produced.

Advantages in Products and Applications

It has been found that the nepheline syenite powder systems describedherein dramatically reduce wear on mechanical equipment. Thus, in oneaspect, the present invention provides a nepheline syenite powder with anovel particle or grain size distribution whereby it greatly reduceswear.

Nepheline syenite powder of the present invention drastically reduceswear on equipment processing the product using the novel inorganicpowder. By providing a grain size distribution not heretofore availablefor nepheline syenite powder the Einlehner Abrasive Value (EAV) issubstantially less than 200 and about 100 or less. Certain powdersystems described herein exhibit Einlehner Abrasive Values of 180-200;70-90; and 15-20.

Another novel aspect of the present invention is its use to obtainproperties attributed only to the novel nepheline syenite powder invarious applications. The new powder has a considerably less abrasiveeffect on equipment than commercially available ultra fine nephelinesyenite powder.

It has also been discovered that the nepheline syenite powder systemsdescribed herein are easily dispersed in resin systems, drasticallyreduce settling, and exhibit a high brightness. By using the powder witha particle or grain size distribution forming an aspect of the presentinvention, coatings can be created by controlled, specific loading ofthe nepheline syenite particle systems to increase clarity, increase theeffect on gloss, and stability of the coating. Consequently, nephelinesyenite powder with a novel particle size distribution has been found toenhance characteristics of the coatings in a manner not obtainable bylarger grain nepheline syenite powder now available.

Nepheline syenite powder having larger particle or grain size has beenused as a filler and/or extender in paint, coatings, plastics, rubberand other materials. The nepheline syenite powder imparts a variety ofphysical properties and technical enhancements to these systems, such asimproved scrub and abrasion resistance in coatings. It has beendiscovered that the novel nepheline syenite powder having controlledparticle size distribution developed as one aspect of the presentinvention offers surprisingly improved levels of optical performancewhile maintaining other critical performance properties of coating.Thus, the novel nepheline syenite powder is particularly beneficial forclear coatings and films.

The particle size material having a particle or grain size distributionas described herein has been proven successful in a coating with thepowder used as a filler or extender, a clear coating, a cured coating, awood coating, a powdered coating including clear coating, automotiveclear coating, coil coating, sealants, paper laminates for pictures andother structures and inks. All of these products have enhanced physicalcharacteristics based upon the use of the nepheline syenite powder withthe novel particle size distribution.

The present invention has resulted in another group of new products thatare enhanced by using nepheline syenite powder with specific sizedistribution with a loading of 10-25% or higher by weight. Theseproducts have used nepheline syenite of a substantially greater grainsize, such as ground nepheline syenite. They have enhancedcharacteristics because they have a high loading of nepheline syenitepowder with controlled size distributions. This class includesultraviolet cured coating, nitrocellulose lacquer, acrylic lacquer,solvent based cured varnish, aqueous coatings such as lacquer, acrylicurethane and other urethane coatings, and 100% solids coatings. Thesecoatings are enhanced by using the nepheline syenite powder describedherein. Additional products in this class of goods improved by using thenepheline syenite powder, other than coatings, are adhesives, sealants,inks and paper laminates for simulated wood of furniture, films,coatings and other structures. They are new and novel because they usethe nepheline syenite powder having a controlled particle sizedistribution.

In accordance with yet another aspect of the present invention, thenovel nepheline syenite powder is used to provide a product from theclass consisting of clear coatings, sealants, paper laminates, aqueouscoatings, solvent based coatings, UV cured coatings, water basedcoatings with resin free pigment paste, nitrocellulose clear lacquer,acrylic lacquer, clear solvent based acid cured varnish, aqueouslacquer, acrylic urethane coating, aqueous clear PUD urethane coatings,100% solids clear UV coatings and powder coatings. Also, the novelnepheline syenite powder is used in a “concentrate”, such as a paste orpredispersant that is incorporated into polymer systems used ascoatings, plastics or rubber articles. The loading or percent of powderadded to the final product is carried by the concentrate into suchproduct.

It has been discovered that the nepheline syenite particle systemsdescribed herein when incorporated into coatings or other formulations,can significantly increase the hardness and resistance of the coating.By using the powder with a particular size distribution forming anotheraspect of the invention, coatings can be created with controlledparticle size distribution to increase block and abrasion resistance,and increase hardness, along with other characteristics.

The present invention also provides substantial physical benefits inclear coatings, powdered coatings, ultraviolet cured coatings and otherapplications which benefits have been realized when compared to variousproducts using commercially available nepheline syenite powder and othercommercial fillers. One of the applications that has been found tobenefit substantially by the use of the novel nepheline syenite powderof the invention is powder coatings, which may be clear or colored.

In accordance with another aspect of the present invention there isprovided another group of commercial or final products including thenepheline syenite powder with a controlled particle size distribution.This group consists of clear liquid wood coating, clear liquid coatingfor flexible substrates, clear liquid coating for rigid substrates, nailpolish, glass, metallurgical slag, refractory fillers, and pigment pasteto make coatings.

A further aspect of the invention is a new product that now includes aspecific nepheline syenite powder with a certain size distribution. Theproduct is selected from the class consisting of opaque liquid coatings,coatings of less than 10 microns in thickness, inks, powder coatings,ceramic bodies, glazes, plastic fillers, rubber fillers, colorconcentrates or pastes and sealants. These products use the nephelinesyenite powder to produce enhanced physical characteristics andproperties as explained herein.

Optical Properties Analysis

Existing and new particle size distributions were formulated in astandard clear acrylic powder coating at Reichhold Chemicals in Durham,N.C. Minex 10 and 12 were used along with new particle size ranges. Thenew particle size ranges tested were 0×2, 0×4, 2×10, 2×6, 4×15, and 6×15microns. This was done to determine the effect of particle size onclarity and gloss. As described below, in terms of gloss reduction andclarity, the midsize ranges 4×15 and 6×15 microns performed the best andtheir use represent a new and novel strategy to reduce the gloss of aclear acrylic powder coating while maintaining good clarity. Previously,powder formulators had to use materials such as waxes to reduce gloss atthe expense of performance. The finer sizes showed the best gloss asexpected, but also had increased yellowness, which was unacceptable. Theability to lower gloss by as much as 50% while maintaining clarity withcontrolled particle size distributions has the potential to open newareas of application for nepheline syenite.

The fillers were compared on an equal weight basis. The formulationswere premixed at 2000 rpm in a Hentchell FM-10 mill for two minutes.This is an initial grinding and mixing stage for powder coatings. Thismixture was then further mixed and melted in a W&P ZSK 30 mm twin screwextruder with zone #1 at 110° C. and zone #2 at 80° C. The materialexits the extruder onto chilled rollers and resembles a ribbon. Thismaterial was then ground in a Retsch Brinkman mill and sieved at −170mesh. The 170 material was then used as the paint material. The coatingswere sprayed onto cold rolled steel and steel penopac panels with atarget final thickness of 1.5 to 2.0 mils (0.0015-0.0020 inches). Thepanels were then baked at 204° C. peak metal temperature for 10 minutes.

Contrast ratio was determined by using black and white penopac panelsthat were coated and measured using a Macbeth Coloreye 3000. Thecontrast ratio is the indication of the difference in the reflectancemeasured over black and white. This measurement was used as an indicatorof haze in a clear coating. New and novel sized nepheline syeniteproducts were tested in a clear powder coating formulation. Measuredcontrast ratios for the tested samples are provided in FIG. 11.Generally, the various new systems exhibited comparable or superiorcontrast ratios as systems of Minex 10 and 12. The effects of particlesize on clarity and gloss were studied and can be found in FIG. 12.

Referring to FIG. 12, the gloss followed generally accepted trends thatthe finer sizes (0×2 and 0×4 microns) will produce a higher gloss, butdid show a bit of yellowing as evidenced in higher b* values from TAPPIbrightness measurements. TAPPI brightness is frequently used as ameasure of the reflectance of papers. The spectral and geometricconditions for TAPPI brightness are specified in TAPPI Method of TestT452, “Brightness of pulp, paper, and paperboard (directionalreflectance at 457 nm),” herein incorporated by reference. The mid-rangegrades 4×15 and 6×15 microns gave excellent results for both clarity andgloss. In this case, a lower gloss is of benefit, as clear coatingsusually have to use additives, such as waxes, to decrease the gloss.This is an important development because maintaining clarity whilelowering gloss is a significant step forward for clear powder coatings.It also appears from the data with the 2×10 and 2×6 microns productsthat the best product for this would be a product in the 4×15 to 6×15microns range.

All the coatings showed similar depth of image results with only slightdifferences. As expected also, the unfilled system had the highest depthof image (DOI) reading.

In powder coatings formulations, it is usually difficult to reduce glossand maintain clarity at the same time. However, with the 4×15 and 6×15microns powders, it was possible to maintain excellent clarity whilegloss was reduced by as much as 50% from the unfilled system.

A research and development program was conducted by Unimin Corporation,the leading manufacturer of nepheline syenite powder. This research anddevelopment program resulted in various novel nepheline syenite powdersas so far described in this application. One embodiment of thedevelopment work related to a nepheline syenite powder having acontrolled maximum particle size and a controlled minimum particle size.In the preferred embodiment of this invention, the maximum particle sizeD99 was about 15 microns and the targeted minimum particle size D5 wasabout 5 microns. This is the 5×15 powder described in this applicationand constitutes the preferred embodiment of the invention defined in theclaims of the parent application. In this same research and developmentprogram, specific work was conducted toward a second inventive conceptand defined in this application wherein the maximum particle size iscontrolled to an extremely low level of less than 5 microns. The twotargeted embodiments of this inventive concept disclosed in theapplication involves a powder with a controlled maximum particle sizetargeted at 4 microns and a controlled maximum particle size targeted at2 microns. This second inventive concept is defined in the claims ofthis divisional application and includes the novel nepheline syenitepowders described as examples 3 and 4 in FIGS. 6 and 7 and shown asgraphs in the chart of FIG. 8. The advantages of these two embodimentsof the second inventive concept in the research and development programare set forth in the explanatory and comparative graphs of FIG. 11 andFIG. 12. The extreme advantage of the second embodiment of the researchand development program is disclosed best in FIG. 12 as having a glosscharacteristic substantially better than other disclosed nephelinesyenite powders. Indeed, it approaches the characteristics of a “blank”sample. The first novel powder of the research and development programis, thus, defined in the claims of the parent application and thealternative or second novel ultra-fine nepheline syenite powder inventedduring the research and development program is claimed in thisdivisional application.

In the initial development project, bulk samples of preprocessednepheline syenite industrial grade #75 were subjected to three differenttypes of commercial ultra-fine grinding mills. These mills and vendorsare listed below.

-   -   1. VibroKinetic Ball Mill (MicroGrinding Systems, Inc., Little        Rock, Ark.)    -   2. Fluid Bed Opposed Flow Jet Mill (Hosokawa-Alpine Micron        Powder Systems, Summit, N.J.). See Konetzka U.S. Pat. No.        6,543,710 which is incorporated by reference herein.    -   3. Vertical Stirred Ball Mill (VSB-M) a.k.a. Attrition Mill        (Union Process Attritor Co., Akron, Ohio). See Szeavari U.S.        Pat. No. 4,979,686 which is incorporated by reference herein.

Each mill was used to produce two products 1) 5×15 microns with a meanparticle size of 7.5 microns and 2) minus 5 microns with a mean particlesize of about 1.2 microns. Distinctions in the test procedures andunique obstacles encountered are discussed below.

Test products were subjected to laser diffraction size analysis with aBeckman Coulter LS 13 320 Particle Size Analyzer. A “Nepheline Syenite”optical model was used instead of a “Fraunhofer” optical model. Inaddition, BET surfaces area measurements and Tappi brightnessmeasurements of each product were made. Scanning electron micrographs,SEM, of select products were also taken.

Vibro-Kinetic Ball Mill—The VibroKinetic Ball mill was operated inclosed circuit with an air classifier.

Fluid Bed Opposed Flow Jet Mill—Hosokawa-Alpine produced the −5 and 2×15micron products by grinding to <15 microns in the Jet Mill and airclassifying this product to remove the minus 5 micron material.

VSB-Mill (a.k.a. Attrition Mill)—Attrition milling can be done eitherwet or dry. This work was done wet, and tests were performed with twodifferent types of attrition mills: 1) a Model 1-S Mill and 2) a Q-2Mill. The 1-S Mill operates in a batch mode and was used to produce thefiner (−5 micron) product. The Q-2 Mill operates in a circulatory mode.This means that the mill product is re-circulated from the bottom of themill to the top. Since finer particles follow a less torturous pathdescending through the media, the coarser particles stay in the milllonger and are preferentially ground. A narrower particle sizedistribution generally results. This mill was used to produce the −15micron product. The Union Process Attritor Co. had no means to classify−5 micron material from the −15 micron product to make a 5×15 micronproduct so a classifier was used.

Size distributions of the products obtained are shown in Table 5.Samples 5 and 6 exhibited a significantly “tighter” or narrowerdistribution than the other samples. Tappi brightness, L*, a*, b* colorvalues, and BET surface area values are shown in Table 6.

TABLE 5 Particle Size Analyses of Processed Nepheline Syenite SampleGrind D_(99,99) D₉₇ D₉₅ D₉₀ D₇₅ D₅₀ D₂₅ D₁ Mean 1 Vibro (−5 μm) 26.2916.48 14.30 10.29 4.90 2.32 1.05 0.42 3.93 2 Vibro (−15 μm) 61.63 22.7218.36 13.22 6.04 2.34 0.87 0.37 5.14 3 Jet (−5 μm) 5.53 4.06 3.83 3.492.92 2.29 1.71 1.10 2.27 4 Jet (−15 μm) 11.60 8.30 7.82 7.00 5.55 4.092.98 2.31 4.40 5 VSB-M (−5 μm) 2.64 1.81 1.66 1.43 0.93 0.52 0.34 0.260.69 6 VSB-M (−15 μm) 11.49 6.43 5.09 3.40 1.99 1.13 0.53 0.32 1.60

TABLE 6 Color and Surface Area Analyses of Ultra-Fine Products Tappi BETBright- Surface Sample Grind ness L* A* b* Area 1 Vibro (−5μ) 81.5092.240 −0.182 3.874 NA 2 Vibro (−15μ) 78.20 91.324 0.067 4.580 NA 3 Jet(−5μ) 87.80 94.312 −0.066 0.452 3.5 4 Jet (−15μ) 87.85 94.075 −0.0880.511 2.3 5 VSB-M (−5μ) 92.44 96.625 −0.125 0.743 17.1 6 VSB-M (−15μ)88.41 94.660 −0.195 0.996 19.0

Vibro-Kinetic Ball Mill—Neither of the products from this mill hadsuitable size distribution (Table 5). The top sizes were too coarse,while the overall distributions were too wide. The brightness results(Table 6) show that the material was discolored, despite the fact thatseveral mill and cyclone liner changes were made to prevent this.

Fluid Bed Opposed Flow Jet Mill—The −5 micron product (Sample 3 in Table5) had an appropriate top size but a greater mean particle size (2.3microns) than the 1.2 micron value that was originally targeted. Thebrightness of this product was nearly 88%. The −15 micron product(Sample 4 in Table 5) had an appropriate top size but a lesser meanparticle size (4.4 microns) than the 7.5 micron value that wasoriginally targeted. The brightness of this product was also 88%.

VSB-Mill (a.k.a Attrition Mill)—Both the nominal −5 and −15 micronproducts (Samples 5 and 6 in Table 5) turned out to be far finer thantargeted. Increased confidence in the new dispersion method, as well asthe BET surface area measurements (Table 6), verified the unexpectedfineness of both products. The brightness values obtained (Table 6) weregreater than those obtained with the jet milled products.

The research and development project as described above resulted in anew level of know-how establishing that the novel nepheline syenitepowder is obtainable by proper selection of manufacturing techniques.The reported initial research and development project resulted in adiscovery of the unique process disclosed generally in FIGS. 1 and 5.Selection of preferred methods was a major development in the nephelinesyenite art and resulted finally in the ability to produce economicallya first novel nepheline syenite powder having a controlled maximum grainsize and a controlled minimum grain size with a very narrow particlesize distribution, and a second novel nepheline syenite powder with anano-size controlled, targeted maximum particle size. Consequently, itwas ultimately learned that the 5×15 powder, the preferred embodiment ofthe first novel powder, could indeed be produced and more importantlyproduced in a manner to become a commercial ultra-fine nepheline syenitepowder. The research and development program as discussed above whichdeveloped the know-how to produce the novel ultra-fine nepheline syenitepowders involved discovery of the criteria that the minimum grain sizeof the novel powder ultimately would involve controlling the final airclassifier stage to operate at a slower feed rate. Furthermore, therewere other process modifications necessary for converting the selectedand invented method of producing the desired nepheline syenite powder.Producing a −5 micron product involved some changes to the airclassifier. It is also contemplated that a Ball Mill could readilyproduce both −5 products, the 0×2 and 0×4 powders. Smaller media wouldprobably be needed. The mill has several systemic features that make itsuperior to earlier generation tumbling mills: 1) its control system, inwhich load cells constantly measure the media charge and load and 2) itsopen circuit air system, which while more expensive, increasesclassifier efficiency by keeping the air temperature at a lower level aswell as at a higher moisture level.

Seven (7) potential grinding aids were considered. The additives werecompared with the results obtained with a control sample, in which thegrinding rate was measured and the times in which a coating of particleswas observed to form on the mill liner (1.5 hours) and mill media (2.0hours) were observed. The time for particle agglomeration to occur (3.0hours) was also noted. The findings were as follows:

Tri-ethanolamine was the best additive. It provided a far fastergrinding rate than the control and no coating was observed on either themill liner or media until after 2.5 hours of grinding. It is also theleast costly additive considered and would be useful for grinding allparticle size ranges. Improved air classifier efficiency is likely usingthis additive.

Other additives that showed promise were a mixture of ethyl alcohol andacetic acid and silicone glycol surfactant.

One additive, ethylene glycol, actually had a negative effect ongrinding.

In this research and development program, the objective was to producecoating filler samples of specific, narrow particle size ranges toenable research to study the effects of particle size on gloss,flatting, and abrasion resistance, particularly in powder coatings.

Powder coatings filler samples were produced using the method of FIGS. 1and 5. A Nissin Engineering, Inc. Model TC-15-NS Turbo Classifier,equipped with a fine rotor for classification in the very fine toultra-fine size range of 0.5-20 microns was used. As is shown in FIG. 1,the classifier also has a microprocessor that provides automaticcalculations of operating conditions. The operator enters the desiredcut size (in microns) and the density (g/cm³) of the mineral beingclassified via a touch screen panel. Then, the microprocessor calculatesthe classifier rotor speed (rpm) and classifier air required (inm³/min). As an example, a 5 microns cut with 2.7-g/cm³ nepheline syeniterequires a rotor speed of 8,479 rpm and an airflow rate of 1.2 m³/min).A schematic of the classification process is shown in FIGS. 1 and 5.

Eleven nominally sized distributions were produced as shown in FIG. 7.

Particle size distribution (PSD) results of the products made with theTC-15-NS Classifier are summarized in Table 7, and grouped as follows:a) PSDs with no minimum bottom size as claimed in this divisionalapplication, b) PSDs with nominal 2 microns bottom size which may beclaimed later, and c) PSDs with nominal bottom sizes of 4 microns to 6microns claimed in the parent application. Complete PSDs of these groupsare plotted in FIGS. 8-10, respectively, with corresponding Sample ID'sshown.

TABLE 7 Actual Size Distributions of Targeted Products Group of TargetActual Size Filler Size D_(99.9) D₉₉ D₉₅ D₉₀ D₇₅ D₅₀ D₂₅ D₁₀ D₅ D₁ Nominimum 0 × 10 10.5 8.93 7.44 6.51 4.79 3.10 1.90 0.73 0.25 0.11 BottomSize 0 × 6 5.83 5.40 4.86 4.48 3.50 2.15 0.64 0.39 0.33 0.26 0 × 4 5.074.63 4.15 2.41 1.78 0.58 0.40 0.32 0.29 0.25 0 × 2 2.74 2.38 1.99 1.741.19 0.70 0.43 0.33 0.29 0.25 Nominal 2-μm 2 × 15 11.7 10.6 9.37 8.546.86 4.67 3.10 2.41 2.16 1.87 Bottom Size 2 × 10 10.7 9.46 7.95 7.055.42 3.79 2.61 1.93 1.65 1.29 2 × 6 6.54 5.70 4.92 4.44 3.60 2.77 2.111.67 1.47 1.21 2 × 4 6.25 5.50 4.63 4.13 3.24 2.36 1.65 1.11 0.31 0.114-μm to 6-μm 4 × 15 17.1 15.7 14.2 13.2 11.2 8.82 6.99 5.78 5.16 2.33Bottom Size 5 × 15 17.1 16.1 14.6 13.7 11.7 9.41 7.46 6.20 5.57 4.68 6 ×15 18.6 17.9 16.1 14.8 12.4 10.1 8.02 6.46 5.72 4.47

The air classifier did a reasonably good job at making the target cuts.Eleven distinct samples were produced for the powder coatings studies.

The Nissin Engineering Model TC-15-NS of FIG. 1 is an excellentlaboratory and small-scale pilot classifier. It is precise, accurate,and relatively easy to operate.

Classification Method (FIGS. 1-12)

The initial research and development project resulted in method A usinga Nissin Engineering Turbo Classifier Model TC-15-N-S as shown in FIG. 1to produce examples (1)-(11) reported in FIG. 6. It was discovered thatthis air classifier operated in a unique manner could produce thedesired nepheline syenite powders constituting the inventive aspect ofthe present invention. Classifier 10 is equipped with a microprocessorthat calculates operating conditions based upon the mineral's specificgravity and the cut off point “x” for producing one extreme of thedesired ultra-fine nepheline syenite powder. Method A disclosed in FIG.1 utilizes the Turbo Classifier 10 in which a feedstock comprising apre-processed nepheline syenite powder, such as a commercial powder or apowder previously processed. Indeed, the feedstock can be a prior run ofthe classifier. The feedstock is introduced as indicated by feedstocksupply or block 12. In the preferred embodiment, pre-processed nephelinesyenite powder is introduced into classifier 10 as indicated by line 14.In one operation, the initial feedstock from supply 12 through line 14is Minex 7 having a controlled maximum particle size or grain sizegreater than 20 microns, but in this instance, less than about 45microns. This pre-processed commercial nepheline syenite powder with acontrolled maximum grain size is introduced into classifier 10 for apurpose of producing various nepheline syenite powders with a first runhaving targeted maximum particle size (D99) distribution and then asubsequent run where “x” is the targeted minimum particle size D5. Thisprocedure produces samples (5)-(11), as shown in the first column ofFIG. 6. Each of these novel ultra-fine nepheline syenite powders have aminimum particle size (D5) controlled by classifier 10 as removed fromcollector 40 as well as a maximum grain size produced in a prior run andremoved from collector 50. This intermediate powder produced by a firstrun through classifier 10 is used for the minimum size run.

Method A using classifier 10 includes a data input block 20 where anoperator inserts the specific gravity of the nepheline syenite powder.The maximum size D99 for examples (5)-(11) and then the minimum size D5for examples (5)-(11) are selectively entered as set value “x.” Datafrom block 20 is directed through line 22 to a microprocessor stage 30.Microprocessor stage 30 sets the classifier air flow and the rotor speedof the classifier. Selected information is provided to the classifierthrough line 32 to operate classifier 10 for controlling first the upperand then the lower grain size of the final powder. During the first runthe cyclone section of classifier 10 separated particles greater thanthe desired minimum particle size value x as set by microprocessor 30.This intermediate powder is deposited into collector or block 40 throughline 42. The intermediate powder with a controlled maximum particle sizeis removed from collector 40 and introduced into supply 12 forreprocessing by classifier 10 with set particle size “x” at the targetedminimum particle size D5 of examples (5)-(11). In this procedure thefinal novel ultra-fine nepheline syenite powder is deposited intocollector or block 50 by line 52. This second operation may require morethan a single pass through the classifier and the particle size value“x” may be progressively reduced. Small fines are discharged fromclassifier 10 into block 60 through line 62.

Classifier 10 employs a classifier disk in accordance with standardtechnology and a cyclone to process the feedstock entering theclassifier through line 14. See English U.S. Pat. No. 4,885,832 for arepresentative description of this known technology. Microprocessor 30controls the air for dispersion and for the classifier as indicated byblock 70. Thus, when examples (5)-(11) shown in FIG. 6 are to beproduced, microprocessor 30 is set for a determined particle size “x”which size is controlled by the rotating rotor disk and the cyclone ofthe classifier. Consequently, in practice nepheline syenite feedstock isclassified by the Turbo Classifier 10 using a combination of theclassifier disk and cyclone. The particle size D99 or D5 is computercontrolled by adjusting the rotational speed of the disk and the airflow over the disk. When setting a specific size, D99 or D5, threefactions are collected. The faction less than the set value “x” which isdirected to collector or block 40. The large faction greater than theset value, is separated by the disk of the Turbo Classifier 10 anddeposited “x” into collector 50. The waste faction is directed to block60 and contains mostly very fine particles but also large particles thatwere not collected by the classifier disk. This waste material isdiscarded.

Classifier 10 is set by an operator by the data input at stage or block20 to control the classifier disk and the cyclone air so that the setparticle size “x” is separated as indicated by either block 40, 50. Ifthe classifier is set to the desired targeted minimum particle size D5,the powder is collected at block 50. If the collected powder is to havea maximum grain size or particle size, it is either previously orsubsequently passed through the classifier again and the data entered atblock 20 is the maximum grain size. The powder is collected from block40. Thus, by both a lower cut and upper cut of particle size byclassifier 10, the novel ultra-fine nepheline syenite powders claimed inthe parent application are produced. Method A is also disclosed in FIG.5 wherein Minex 4 is the feedstock introduced into the feed hopper orblock 12 for the first run of classifier 10A, 10B. Minex 4 has a maximumgrain size controlled at about 60 microns. However, an alternatepre-processed nepheline syenite powder initial feedstock (Minex 7) witha maximum grain size of about 40 microns is also contemplated. Minex 4and Minex 7 are not defined as “ultra-fine” nepheline syenite powder,which is a powder having a maximum grain size less than about 20microns. The substantial advantages of “ultra-fine” nepheline syenitepowder have been recently discovered and are known in the art,especially when the ultra-fine nepheline syenite powder is used as afiller in coatings or films.

Operation of method A as described in FIGS. 1 and 5 is used to produceultra-fine nepheline syenite powder with various targeted sizes as setforth in the novel samples (5)-(11) of FIG. 6. The targeted sizes haveresulted in the actual particle size distributions recorded in table ofFIG. 6. Method A is the first preferred embodiment of a type of processdiscovered to be useful in practicing the invention claimed in theparent application, which invention relates to an ultra-fine nephelinesyenite powder having a controlled minimum particle size D5 and, in thepractical embodiments of the invention, having a controlled maximumparticle size D99. Referring now to the actual particle sizedistribution for targeted samples (5)-(11) described in FIG. 6, thereare eleven different powders samples identified as samples (1)-(11) andmade by method A. The first four samples (1)-(4) of powders processed bymethod A have targeted maximum grain size D99, but have no controlledminimum grain size D5. Samples (3)-(4) is produced by the classifierused in method A and constitutes a powder within the definition of thepresent invention. These related samples, i.e. samples (3)-(4), have agrain size distribution recorded in FIG. 6 and shown in the curves inFIG. 8.

As indicated in this description, one broad concept of the newultra-fine nepheline syenite powder is control of the minimum grain sizeto create a narrow particle size spread. The secondary aspect of thisfirst invention claimed in the parent application is control of themaximum grain size. Samples (5)-(8) of FIG. 6 are embodiments of onenovel ultra-fine nepheline syenite powder. The minimum particle size ofthe samples is targeted at 2 microns with the created spread of lessthan about 12 microns (such as example 5). However, the samples have theactual distribution shown in the curves of FIG. 9. All of these novelnepheline syenite powders have a targeted minimum particle size D5 of 2microns. Classifier 10 accurately controls the minimum size, but is lessaccurate in merely letting the powder taper randomly to a zero level atD1 as in samples (3)-(4). Samples (5)-(11) have been processed by methodA to have a maximum controlled grain size D95 or D99, which is thesecond aspect of the invention. Controlling the top and bottom particlesizes of a sample results in control of the narrow particle sizedistribution of the invention. Sample (5) has a targeted maximumparticle size of 15 microns. The other samples (6)-(8) have controlledminimum particle size of 2 microns and a controlled maximum grain sizeD95 or D99 of 10, 6 and 4 microns, respectively. These samples are shownin the curves of FIG. 9. In accordance with the preferred implementationof the first invention, the minimum particle size is controlled in thegeneral range of 4-7 microns as set forth in samples (9)-(11) of FIG. 6.However, the minimum grain size is in the range of 2-7 microns under thefirst invention. These preferred implementations of the presentinvention, samples (9)-(11) have a controlled maximum particle size ofabout 15 microns and have the actual grain size distribution as shown inthe table of FIG. 6 and in the graph of FIG. 10. In summary, theclassifier 10 can be used to control the maximum particle size of thenepheline syenite powder as in samples (3)-(4) constituting theinvention claimed in this divisional application. However, in accordancewith the first invention classifier 10 is used in method A to produce anultra-fine nepheline syenite powder where the minimum particle size iscontrolled to give a narrow particle size distribution. This concept ofcontrolling the lower grain size of the nepheline syenite powder iscombined with controlling the maximum particle size of the nephelinesyenite powder as in samples (5)-(11). These samples have the targetedparticle sizes and the actual particle size distribution provided inFIG. 6 and illustrated in the particle size distribution curves of FIGS.9 and 10.

Method A can be operated to produce the novel ultra-fine nephelinesyenite powder by performing the steps set forth in FIGS. 2 and 3.Method A, as shown in FIG. 2, is used to produce samples (5)-(11) asdisclosed in FIGS. 6 and 7. A commercial grade of nepheline syenitepowder having a maximum particle or grain size greater than about 30 or40 microns is introduced as the feedstock in hopper 12 as indicated byblock 100. Since this material, which may be Minex 4 or Minex 7, has arelatively large controlled maximum grain size, it is first passedthrough classifier 10 as indicated by block 102 to control the minimumparticle size. Thereafter, it is passed through classifier 10 to controlthe maximum grain size as indicated by block 104. This procedure makes apowder as indicated by block 110. The two classifying stages arenormally reversed. If a 15 micron controlled maximum particle size isdesired for the novel ultra-fine nepheline syenite powder, thecommercial, pre-processed powder Minex 10 could be used as thecommercial feedstock, as shown in block 112 in FIG. 3. The feedstock hasthe desired maximum particle size and is merely passed through theclassifier set to remove the smaller particles. The minimum particlesize is established, as indicated by block 114 of FIG. 3. This procedureproduces samples (12)-(15), as described in connection with FIGS. 6 and7. The maximum grain size is controlled by the inherent maximum particlesize of incoming commercial feedstock, i.e. Minex 10. The feedstockitself has the desired controlled maximum particle size of about 15microns. Turning now to the alternative method disclosed in FIG. 4,classifier 10 is used to produce an ultra-fine nepheline syenite powderby merely removing the particle sizes above a given value. Such powderdoes not result in creation of an ultra-fine nepheline syenite powderwith a controlled minimum particle size. FIGS. 2-4 are disclosed sincethey represent various operations of method A to make ultra-finenepheline syenite powders. If it is desired to remove only particle sizebelow a minimum value, then the maximum controlled grain size isdetermined by the maximum particle size or grain size of the incomingcommercial feedstock. Consequently, Minex 4 or Minex 7 could not be usedas the commercial feedstock for such method. In this process, thecommercial feedstock must have a maximum grain size sought for the finalpowder. This is illustrated in FIG. 3.

To show properties of the invention, the nepheline syenite powderdisclosed in FIGS. 6 and 7 was formulated in a clear acrylic powdercoating. This is to determine the effect of the particle size of theinventive powder or clarity in gloss. In terms of gloss reduction andclarity the powder with a minimum particle size of 4 and a maximumparticle size of 15 (4×15) or a minimum size of 6 and a maximum size of15 (6×15) performed the best and represent a new and novel way to reducethe gloss of a clear acrylic powder coating while maintaining goodclarity. Previously, powder forming a filler had to be combined withmaterial, such as wax, to reduce gloss. This was at the expense ofperformance. The ability to lower gloss by as much as 50% whilemaintaining clarity with controlled particle distribution size, as inthe present invention, has resulted in opening new areas of applicationfor nepheline syenite powder. To counteract the effect of lowering glosswhile maintaining clarity in acrylic powder coating, various powdershaving the novel features were compared with other fillers in acrylicpowder coating. Powders of the present invention were compared to thevalues obtained by Minex 10 and Minex 12. Minex 10 and Minex 12 are both“ultra-fine” nepheline syenite powders, but they have no control overthe minimum particle size. In the test procedure, coatings with variousfillers were sprayed onto cold rolled steel. Steel panels with a coatinghaving a target final thickness of 1.5-2.0 mils were produced. Thepanels with the various coatings were baked at 204° C. each for tenminutes. The contrast ratio was determined by using black and whitepanels that were coated and measured with a Macbth Coloreye 3000. Thecontrast ratio is indication of the difference in the respectivemeasurement over black and white. This measurement was used as anindicator of the haze in a clear coating. The new and novel nephelinesyenite powders were tested in a clear powder coating. The mid sizepowder as mentioned before gave excellent results for both clarity andgloss. As indicated, lower gloss is a benefit in clear coatings becausethey usually have to use additives, such as waxes to decrease the gloss.This is an important development because maintaining clarity whilelowering gloss is a significant step forward for clear powder coatings.The results of these comparisons are shown in FIGS. 11 and 12 as alreadydescribed. In summary, the novel nepheline syenite powders maintainexcellent clarity while gloss was reduced by as much as 50% from theunfilled system.

Milling and Classifying Methods (FIGS. 13-19)

The ultra-fine nepheline syenite powder of the invention claimed in theparent application involves control of both the minimum particle sizeand the maximum particle size of a feedstock which has been convertedfrom a pre-processed commercial powder. As discussed previously, apreferred method of producing such novel powder involves the use of anopposed air jet mill followed by a classifier or an attrition milloperated in a dry mode followed by an air classifier. The dry millgrinds the incoming pre-processed nepheline syenite powder feedstockinto a powder having reduction in the maximum particle size. This is thenormal operation of a mill; however, in accordance invention claimed inthe parent application, the mill for reducing the maximum grain size isused to produce a powder where the maximum grain size is a value lessthan about 20 microns. Thus, the resulting dual processed nephelinesyenite powder is “ultra-fine”. This subsequently milled pre-processedpowder feedstock is converted into an intermediate powder with acontrolled maximum particle size. Then the intermediate powder is passedthrough an air classifier to obtain the targeted minimum particle sizeso that the resulting powder is new and is an ultra-fine nephelinesyenite with both a controlled maximum particle size and a controlledminimum particle size. This process produces a narrow particle sizedistribution. This dual process creates a powder having the advantageousimproved characteristic of the new powder. Of the many technologiesinvestigated to produce the new nepheline syenite powder, the firstpreferred implementation was the classifying method A disclosed in FIGS.1 and 5. It has been found that the preferred practical embodiment ofthe invention involves the use of a mill to dry grind pre-processednepheline syenite powder feedstock having a controlled grain sizesubstantially greater than 20 microns and less than 100 microns.

This second preferred embodiment or practical implementation of theinvention claimed in the parent application is method B disclosed inFIG. 13. Method B involves use of Industrial Grade 75 pre-processednepheline syenite feedstock having a controlled maximum particle size ofabout 60 microns. The maximum particle size D99 of this feedstock isabout 60 microns to produce the controlled particle size of thenepheline syenite powder. Industrial Grade 75 has no controlled minimumparticle size, but the particle size of this feedstock merely convergestoward zero at D1. Method B involves the use of an opposed air jet millfrom Hosokawa Alpine and sold as AFG Model 400. This opposed air jetmill 202 is the second preferred mill used in practicing the inventionof the invention claimed in the parent application and is illustrated asthe mill for method B shown in FIG. 13. Such mill is schematicallyillustrated in Zampini U.S. Pat. No. 5,423,490 and Konetzka U.S. Pat.No. 6,543,710, which are incorporated by reference herein. Thisfluidized bed opposed jet mill use air jet mill for grinding thefeedstock. As compressed air exits internal nozzles, it is acceleratedto extremely high speeds. In expanding, the energy contained in thecompressed gas is converted to kinetic energy. The velocity of the airexiting the Laval nozzle or nozzles exceeds the speed of sound. The airis the grinding gas. Gas and powder from the fluidized bed is comminutedas the result of interparticle collision of the air jets, especially inthe areas where opposed jets intersect. The fluidized bed opposed jetmill has a dynamic deflector-wheel classifier so the fineness of theparticles is a function of the wheel speed. See Zampini U.S. Pat. No.5,423,490 for a jet nozzle design. The feedstock is ground by mill 202set to the targeted maximum particle size which in the illustratedembodiment is 15 microns. This opposed jet mill is disclosed in FIG. 13Aand directs ground nepheline syenite powder through line 202 a to an airclassifier 204, which classifier, in the preferred embodiment, is anAlpine Model 200 ATP. Feedstock enters the classifier as the classifierair flows through the rotating classifying wheel. This wheel extractsfines and conveys them by air from the classifier. The coarse materialis rejected by the classifying wheel and exits the lower discharge valvefor the powder that has a controlled minimum particle size. This airclassifier is set to remove particles having a size less than thetargeted minimum particle size. Product passing through lines 204 a iscollected as indicated by block or collector 210. Method B is developedprimarily for producing the novel ultra-fine nepheline syenite powdersidentified as samples (5)-(11) illustrated in FIG. 6. In therepresentative use of method B illustrated in FIG. 13, 5×15 sample (10)is produced. However, method B is also applicable for the other examplesmentioned and, indeed, to produce the other samples of the invention asset forth in FIGS. 6 and 7.

An opposed air jet mill performs the dry grinding function of block 202in FIG. 13. This device is schematically illustrated as opposed air jet220 in FIG. 13A. Mill 220 accepts pre-processed nepheline syenitefeedstock from block or supply 200 and directing the feedstock intohopper 222. The feedstock has a maximum particle size previouslyimparted to the commercial feedstock powder. This maximum particle sizeis in the general range of 20-150 microns. The commercial feedstockenters mill 220 through feed hopper or funnel 222 and is then conveyedinto the mill by the compressed air or gas inlet 224 from a supply ofcompressed air or gas 226. To grind the incoming feedstock compressedgrinding air is introduced into the mill through inlet 230 connected toa compressed grinding air source 232. In accordance with this type ofcommercially available grinding mill, as already explained, there is agrinding chamber 240 where the feedstock is subject to high speed airjets. The chamber has a replaceable liner 242 and a grinding airmanifold or recirculating air chamber 244. Ground particles having areduced grain size from the feedstock are directed to outlet 260surrounded by a vortex finder 262. The ground particles P aredrastically reduced in size from the incoming feedstock FS. Thecommutation or grinding is performed by the opposed air jets in chamber240. In one use of mill 220, the particles exiting from outlet 260 hasthe desired maximum particle size, i.e. the targeted D99 size. Inanother use of mill 220, there is a classifier set at the maximumparticle size and the ground powder from outlet 260 is larger, but issubsequently classified to the desired maximum particle size. In theequipment used in method B, mill 220 has a variable speed internalclassifier wheel which is adjusted to separate particle sizes less thana desired target size. The separated particles exit by gravity throughline 202 a into a collector 202 b. Particles in line 202 a shown in theillustrated embodiment of the invention have a maximum grain size of 15microns. Particles having larger particle size, but entering into theclassifier 270 from outlet 260 are directed through line 272 back intothe grinding chamber with incoming feedstock FS at funnel or hopper 222.Powder from the classifier wheel enter line 202 a and is deposited incollector 202 b. The powder has a controlled maximum particle size. Itis then bagged and introduced into air classifier 204, as indicated bydashed line 202 c. The opposed air jet mill is the preferred dry millused in practicing method B as shown in FIG. 13. However, before adisclosure of an implementation of method B shown in FIG. 13, a genericversion of this method is method C illustrated in FIG. 14.

Method C uses a pre-processed commercial feedstock having a maximumcontrolled grain size of less than about 45 microns. This feedstock iscommercially available as Minex 7 from Unimin Corporation. Feedstockfrom supply 300 is directed through feed line 302 into a dry mill 304.This mill can be an attrition vertical stirred dry mill in a closedcircuit or, preferably, an opposed air jet mill as used in the secondpreferred embodiment of the invention as shown in FIG. 13. Thus, methodC is a generic version and employs a dry mill 304 that produces a powderhaving a maximum particle size matching a selected maximum targetedparticle size. This intermediate powder is transferred to line 306. Thedry mill normally combined with an air classifier and having a coarsepowder return indicated schematically as line 304 a. As an alternativemill 304 grinds the feedstock and directs its output to an internalclassifier and then to line 306. Irrespective of the dry milling step304 of method C, the output of the dry mill and/or air classifier is theintermediate powder in line 306. This intermediate powder is directed toair classifier 308 that removes particle sizes less than the targetedminimum particle size. In the illustrated embodiment this D5 target is 5microns. From air classifier 308, the desired ultra-fine nephelinesyenite powder is directed by line 308 a into a collector 310. Theproduct is identified as a 5×15 powder having a targeted maximumparticle size D99 of 15 microns and a targeted minimum particle size D5of 5 microns. Process C is, indeed, a generic version of the preferredembodiment illustrated in FIG. 13; however, it also includes anauxiliary process operation. Minex 12 has only a maximum particle size.Fine nepheline syenite powder from air classifier 308 is directedthrough line 308 b into an air classifier 322 set to remove particlesgreater than the maximum particle size. Thus, classifier 322 essentiallydirects the material from line 308 b into collector 320 for subsequentuse as Minex 12 with only a controlled maximum targeted particle size.

The first and second preferred methods developed for producing a novelultra-fine nepheline syenite powder are the types of process used inmethods A and B, the latter of which is generically disclosed as methodC. For completeness, the research and development program also inventedalternative methods for making the novel ultra-fine nepheline syenitepowder claimed in the parent application. These alternative methodsconstitute further advances in the nepheline syenite powder art of thenepheline syenite industry. One alternative is disclosed in FIG. 15.Method D utilizes a pre-processed. Commercial nepheline syenite powderfeedstock, such as Minex 7 having a controlled maximum particle size ofabout 45 microns. This commercial feedstock from supply 330 is conveyedby line 332 into a first air classifier 340 that operates in accordancewith somewhat standard practice in separating from the feedstock anyparticle having a maximum particle size of a targeted amount,illustrated as 15 microns. This operation of an air classifier createsan intermediate powder that is conveyed through line 342 into second airclassifier 350. Air classifier 350 is a second classifying stage andremoves particles having a size less than the targeted minimum particlesize, illustrated as 5 microns. By using the two stage air classifierconcept of method D, the desired novel ultra-fine nepheline syenitepowder is directed to collector 360 through line 362. By using the dualor two stage air classifier process, a desired nepheline syenite powderis produced and deposited in collector 360. In practice, the airclassifiers 340, 350 are Alpine Model 200 ATP. Another appropriateclassifier is shown in Saverse U.S. Pat. No. 4,551,241 and English U.S.Pat. No. 4,885,832. These patents are incorporated by reference herein.Intermediate powder from line 342 is directed into the feed inlet airflow line of second air classifier 350. Consequently, the intermediatepowder from the first stage air classifier 340 moves into the secondstage air classifier 350. The intermediate powder is directed into theclassification chamber of classifier 350 where the lighter smallparticles float upward into the variable speed classifier wheel and arediscarded. The coarse material falls downward into a collection drum orcollector 360. Thus, the product in collector 360 is a product havingboth the targeted maximum particle size and the targeted minimumparticle size. Other aspects of the development project resulting in thepresent inventions are schematically illustrated in FIG. 15. Method D ismodified as indicated to perform method D′. In this modified procedure,second stage air classifier 350 is replaced by second stage airclassifier 350 a, which is set to a different targeted minimum particlesize D5. This setting has been 4 microns and the disclosed 6 microns.Another modification of method D is illustrated as method D″. In thisalternative method to make the invention claimed in the parentapplication two separate classifiers 370, 380 are operated in series togradually increase the minimum particle size of the novel powderultimately deposited in collector 360. Methods D, D′ and D″ are allmultiple stage classifier methods to produce the novel nepheline syenitepowder as so far described and generally set forth in FIGS. 6 and 7.Method B described in FIGS. 13 and 14 is now the preferred method usedfor making samples with a targeted minimum particle size and a targetedmaximum grain size of the type illustrated in FIGS. 6 and 7 and alsospecifically illustrated as samples (20) and (21) in FIG. 18. Toillustrate that the maximum particle sizes is “controlled” as in methodsA, B and C, samples (20) and (21) of FIG. 18 have an upper particle sizecut off to a particular maximum particle size. This control of themaximum size of samples (20)-(21) is indicated by lines 280 and 282.

Powder samples (12)-(15) listed in the table of FIG. 7 have beendescribed as powders that could be made by removal of only particlesbelow the targeted minimum particle size D5; however, in practice thesepowders are actually produced by the methods that control the maximumparticle size also. In other words, previously described samples(12)-(15), which were identified as controlling only the minimumparticle size, are preferably produced by controlling both the minimumparticle size and also the maximum particle size. Samples (12)-(15) canbe made by either cutting both the top and bottom particle sizes orstarting with an ultra-fine commercial powder and cutting only thebottom particle size. This latter process is indicated as samples(16)-(19) in the graph of FIG. 17. In summary, it is within the broadestscope of the invention claimed in the parent application to produce thenovel ultra-fine nepheline syenite powder with a controlled minimumparticle size by starting with a pre-processed commercial ultra-finenepheline syenite powder, such as Minex 10, having a controlled maximumparticle size of about 15 microns. This is generally disclosed in FIG. 7and specifically presented in FIG. 17. To complete this description, amethod for practicing the present invention process by the act ofcontrolling only the minimum particle size is disclosed as method E inFIG. 16. This further method involves using a specific commercialnepheline syenite feedstock, which is already “ultra-fine” and has acontrolled maximum particle size in the range of 13-18 microns. Minex 10with a controlled maximum particle size of 15-20 microns is directedfrom supply 370 through line 372 into classifier 380. Classifier 380 isset to remove smaller particle sizes so that the minimum particle sizeof the powder is controlled. Such powder is directed through line 382into collector 390. Thus, in this particular alternative method, anultra-fine nepheline syenite powder is merely processed by a classifierthat removes all particles having a size less than x microns. In thesample illustrated in FIG. 17 the set size is 4, 6 or 8 microns. In theillustrated embodiment of this alternative method, the set particle sizeis 5 microns. These samples of the novel nepheline syenite powder aremade by the method E. If the maximum particle size needs particlecontrol, methods A-D are used for these samples. The preferred samplesof this particular novel ultra-fine nepheline syenite powder (4×15, 5×15and 6×15) is set forth in the curves of FIG. 19 and constituting samples(9)-(11) respectively of FIG. 6. In these curves, the D50 particle sizeis less than 10 microns. This provides low tendency to settle and hightransparency.

Small Particle Size Alternative

Parent provisional application Ser. No. 60/958,757, filed Jul. 9, 2007(UMEE 2 00090 P; UNM-19913) was incorporated by reference in co-pendingapplication Ser. No. 12/215,643 filed Jun. 27, 2008 from which thisapplication is a continuation. Provisional application 60/958,757 (UMEE2 00090 P; UNM-19913) is incorporated by reference herein since itstresses an alternative to the embodiment described in FIGS. 13-19.

The broad invention relates to “controlled particle size distribution”of an inorganic powder formed from a hard, naturally occurring minedmaterial having substantially no free silica, in particular nephelinesyenite powder, used as a “hard filler.” The first embodiment is thelarger 5×15 powder and the alternative is the −5 powder where thetargeted maximum particle size is less than 5 microns, i.e. examples of2 microns and 4 microns.

One type of new powder was a powder with a “zero” bottom size andcontrolled top size as used in the −5 powder. Two controlled top sizeswere 2 microns and 4 microns in the −5 powder alternative development.Classification of powder in both embodiments defines “fines” asparticles less than 0.5 microns.

In the alternative powder, described as the −5 powder, the powder has“targeted” sizes of 0×2 or 0×4. The targeted 2 microns maximum particlesizes and the targeted 4 microns maximum particle size are defined asthe top cut particle sizes or the −5 powder. These powders have “Nominimum bottom size.”

The actual top cut particle size of the targeted 0×2 particle size isD99.9 of 2.74 microns, D99 of 2.38 microns and D95 of 1.99 microns. TheD1 particle size is 0.25, while the D5 particle size is 0.29. These“zero” targeted particle sizes merely have “fines” removed.

The actual top cut particle size of the targeted 0×4 particle size isD99.9 of 5.07 microns, D99 of 4.63 microns and D95 of 4.15 microns. TheD1 particle size is 0.25 microns and the D5 particle size is 0.29microns. These “zero” targeted particle sizes merely have “fines”removed.

Powder with no minimum bottom size is shown by the graphs 2, 3, 4 inFIG. 8 of this application. The targeted controlled particle size of 0×2microns had the lowest tested Einlehner number of 16.9. This number is ameasure of abrasive action on processing equipment and is very importantwhen using fillers made from a hard rock, such as nepheline syenite.

In a first run of nepheline syenite powder having a “target size” of 4microns, the D99 particle size was 4.6 microns. In a second run ofnepheline syenite powder having a “target size” of 2 microns, the D99particle size was 2.4 microns.

The 0×4 and 0×2 powders (i.e., the −5 powder alternative invention)“have better light gathering and transmittance properties.” The “0×4size has noticeably greater light transmittance properties.”Furthermore, the −5 powder alternative invention is useful for obtainingdeeper cure in UV cure coatings.” “Optical clarity was best for the 0×2followed by 0×4 size range.” Optical clarity “improves with finerparticle size.”Overall, the 0×4 and 0×2 show more performanceimprovements and results suggest they can even benefit UV cure oraccelerate UV cure time.”

Minex 0×2 powder and Minex 0×4 powder (the −5 powder alternativeinvention) “result in the least scattering of light.”

The preferred method of producing the alternative −5 micron powder (0×2and 0×4) is disclosed as using a vertical stirred ball mill (VSB)operated in a wet mode. This mill was an S-1 mill from Union ProcessAttritor Company of Akron, Ohio. The −5 microns powder was Sample53-36-3 having a targeted top size of 2 microns and an actual top sizeD99.99 of 2.64 microns. This is the 0×2 powder version of the −5 micronspowder. A fluid bed opposed flow jet mill produced Sample 53-38-1 with atargeted 4 microns top size with an actual top size D99.99 of 5.53microns. These values are shown in Table 5. This is the 0×4 powder ofthe −5 powder alternative.

In summary, the provisional application discloses a preferred method ofproducing the alternative −5 micron powder as using vertical stirredball mill, with or without a grinding aid, but preferably operated in a“wet mode.” The powder is preferably marketed as a “slurry”, but is alsoto be marketed dry if needed. As an alternative, the −5 powder isproduced by a fluid bed opposed jet mill operated in a dry mode andclassified by an air classifier.

1. An ultra-fine inorganic powder for use as a filler and formed from ahard, naturally occurring mined material having substantially no freesilica, said powder having a targeted controlled maximum particle sizeof less than 5 microns and a generally uncontrolled minimum particlesize creating a targeted minimum particle size of zero microns.
 2. Anultra-fine powder as defined in claim 1 wherein said powder has a Mohsnumber of
 6. 3. An ultra-fine powder as defined in claim 1 wherein saidpowder contains the mineral feldspar.
 4. An ultra-fine powder as definedin claim 3 wherein a majority of said powder contains at least onefeldspar mineral.
 5. An ultra-fine powder as defined in claim 3 whereinsaid powder is syenitic.
 6. An ultra-fine powder as defined in claim 1wherein said powder is syenitic.
 7. An ultra-fine powder as defined inclaim 3 wherein said powder is nepheline syenite.
 8. The ultra-finenepheline syenite powder defined in claim 7 wherein said powder has aD99 particle size of less than 5 microns.
 9. The ultra-fine nephelinesyenite powder as defined in claim 8 wherein said powder has a D99particle size in the range of about 2 microns to about 4 microns. 10.The ultra-fine nepheline syenite powder as defined in claim 7 whereinsaid powder has a D99 particle size in the range of about 2 microns toabout 4 microns.
 11. The ultra-fine nepheline syenite powder as definedin claim 7 wherein said targeted maximum particle size is in the generalrange of 2-4 microns.
 12. The ultra-fine nepheline syenite powder asdefined in claim 8 wherein said powder is produced in vertical stirredmill.
 13. The ultra-fine nepheline syenite powder as defined in claim 12wherein said vertical stirred mill is operated in the wet mode.
 14. Theultra-fine nepheline syenite powder as defined in claim 7 wherein saidpowder is produced in vertical stirred mill.
 15. The ultra-finenepheline syenite powder as defined in claim 14 wherein said verticalstirred mill is operated in the wet mode.
 16. The ultra-fine nephelinesyenite powder as defined in claim 11 wherein said powder is producedfrom a pre-processed nepheline syenite powder with a maximum particlesize D99 in the range of 20-100 microns, and a moisture content of lessthan 0.8% by weight.
 17. The ultra-fine nepheline syenite powder asdefined in claim 8 wherein said powder is produced from a pre-processednepheline syenite powder with a maximum particle size D99 in the rangeof 20-100 microns, and a moisture content of less than 0.8% by weight.18. The ultra-fine nepheline syenite powder as defined in claim 7wherein said powder is produced from a pre-processed nepheline syenitepowder with a maximum particle size D99 in the range of 20-100 microns,and a moisture content of less than 0.8% by weight.
 19. The ultra-freenepheline syenite powder as defined in claim 7 wherein said powder has aparticle size distribution with a narrow particle size spread betweenthe D99 particle size and the D1 particle size.
 20. The ultra-finenepheline syenite powder as defined in claim 19 wherein said D99particle size is in the range of about 2-4 microns.
 21. The ultra-finenepheline syenite powder as defined in claim 9 wherein the targetedmaximum particle size is a D99 particle size of about 2 microns.
 22. Theultra-fine nepheline syenite powder as defined in claim 7 wherein thetargeted maximum particle size is a D99 particle size of about 2microns.
 23. The ultra-fine nepheline syenite powder defined in claim 7wherein the targeted maximum particle size is a D99 particle size ofabout 4 microns.
 24. A filler for a coating comprising an ultra-finenepheline syenite powder as defined in claim
 9. 25. A filler for acoating comprising an ultra-fine nepheline syenite powder as defined inclaim
 7. 26. A coating comprising a filler as defined in claim
 25. 27. Acoating comprising a filler as defined in claim
 24. 28. An ultra-finenepheline syenite powder having a targeted controlled maximum particlesize of less than 5 microns and a generally uncontrolled minimumparticle size of zero microns, wherein the D50 particles size of saidpowder is less than 1 micron.
 29. The ultra-fine nepheline syenitepowder as defined in claim 28 wherein said maximum particle size is inthe general range of about 2-4 microns.
 30. The ultra-fine nephelinesyenite powder as defined in claim 28 wherein said maximum particle sizehas a targeted particle size of about 2 microns.
 31. The ultra-finenepheline syenite powder as defined in claim 28 wherein said maximumparticle size has a targeted particle size of about 4 microns.
 32. Anultra-fine inorganic powder for use as a filler and formed from a hard,naturally occurring mined material having feldspar as its major mineraland having substantially no free silica, said powder having a targetedcontrolled maximum particle size of less than 5 microns and a generallyuncontrolled minimum particle size creating a targeted minimum particlesize of zero microns.
 33. An ultra-fine powder as defined in claim 32wherein said powder is syenitic.
 34. An ultra-fine powder as defined inclaim 33 wherein said powder is nepheline syenite.
 35. The ultra-finenepheline syenite powder defined in claim 32 wherein said powder has aD99 particle size of less than 5 microns.
 36. The ultra-fine nephelinesyenite powder as defined in claim 35 wherein said powder has a D99particle size in the range of about 2 microns to about 4 microns.